請觀音經疏闡義鈔 2.61

2.61

經「寶積」者，觀心雖空，具足萬行。萬行眾寶積之於理，故云寶積。

The sūtra says "Ratnakūṭa" (Jewel Accumulation): although the contemplating mind is empty, it is fully equipped with the myriad practices. The myriad practices and manifold jewels are accumulated in the principle; hence it is called Jewel Accumulation.